Photovoltaic (“PV”) panels or modules are generally fabricated with multiple substrings of PV cells connected in series to convert solar insolation to electric power. The PV modules have traditionally been manufactured as independent components that employ a power converter (also referred to as a “power subsystem”) in each PV module to independently control a module operating characteristic, particularly for providing maximum power point tracking (“MPPT”). A direct current (“dc”) power generated by each PV module is generally converted to alternating current (“ac”) power in a central power converter for connection to a local utility grid.
The overall electrical performance of a PV module such as the efficiency to convert solar insolation to electrical power is a performance metric that depends on multiple factors. One factor is MPPT that ensures that each PV module operates at a voltage and current to maximize electrical energy at a particular level of solar insolation. Ensuring MPPT across the power converters for multiple PV modules or across the power converters for multiple substrings of PV cells within a PV module can be a challenging design task. To perform MPPT, a control loop is generally employed to measure locally produced current and voltage to properly adjust, for example, a duty cycle of a power train of the power converter for MPPT. In addition to local control, however, it would be advantageous to implement hierarchal control for a plurality of PV modules, multiple substrings of PV cells of a PV module, and/or each PV cell for the multiple substrings of PV cells to augment the performance of a power system such as a PV system.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the preferred embodiments and are not necessarily drawn to scale.